1. Field of the Invention
The present invention relates to an image processing technique for altering a display in accordance with a surrounding environment.
2. Description of the Related Art
The perceived color of a real object changes with the observation direction and the light source direction. One reason for this is that the gloss component changes with the observation direction and the light source direction. Specific examples of the gloss component include a light source image reflected on a real object, and a surrounding environment image reflected on a real object. It is also known that an interference color of light produced by a thin film, or coloration attributable to a microstructure such as the wings of a Morpho butterfly (hereinafter referred to as structural color) also cause the perceived color to vary with the observation direction and the light source direction.
In generating an image of a virtual space, there is a known method for reproducing gloss according to a light source placed inside the virtual space and a viewpoint placed inside the virtual space. One example is a method in which light ray tracking or photon mapping is used to calculate the amount of light that reaches a viewpoint. Environment mapping is also known as a way to reproduce the reflection of the surrounding environment. In environment mapping, a viewpoint and a surrounding environment texture image are placed inside a virtual space, and the viewpoint and the angle of virtual object surfaces are used to reproduce the reflection of the surrounding environment in the virtual object. For example, with a technique disclosed in Japanese Patent Laid-Open No. 2003-99801, glare and reflection of the surrounding landscape on a real object are reproduced according to previously produced surrounding landscape data and data about the light source placed according to user instructions.
As discussed above, the perceived color of a real object changes with the observation direction and the light source direction. However, there was no known method for reproducing on a display apparatus such a change in the color of a real object that depends on the observation direction and the light source direction. For example, the method disclosed in Japanese Patent Laid-Open No. 2003-99801 is a method for generating a virtual space image according to a viewpoint and a light source placed at specified positions within a virtual space, but cannot reproduce the change in the color of a real object that depends on the observation direction and the light source direction in a real space.